LEAD-COVERED PAPER-INSULATED TELEPHONE CABLE 455 



5500 lb. per sq. in. The four steel columns supporting these top 

 castings are 12^ in. in diameter. The steel ram e.xerts during extrusion 

 a pressure of approximately 59,000 lb. per scj. in. on the lead. At the 

 floor level of the press there is a cast-steel plate which carries a steel 

 spacing block upon which the die block rests. Above the die block is a 

 water-jacketed lead cylinder which is exactly centered over the feed 

 orifice of the die block. The die block and lead cylinder are held in place 

 on the cast-steel plate by four 2\ in. bolts. All these parts are station- 

 ary on this press, facilitating handling and inspection, and insuring that 

 the cable core always enters and leaves the die block at the same angle. 



Fig. 23 — Lead press hydraulic pumps. 



The concentricity of the sheath is affected not only by the contour 

 of the extrusion chamber, including core tube and die, but also by the 

 manner in which heat is applied; and the thickness is affected by 

 temperature and speed of extrusion so that the human element is an 

 important factor, and it is necessary to have thoroughly trained and 

 reliable operators on this kind of work. Temperature indicators are 

 used to show die-block temperatures, and the temperature of the 

 molten lead is automatically controlled and recorded. 



Aside from increasing output, many studies have been made to 

 determine the exact mechanism of lead extrusion, the relative flow of 

 lead in dift'erent parts of the extrusion block, the effect of application 

 of heat at different points, etc. 



As the lead-covered cable leaves the press, it is wound upon either 



